The proliferation of mobile, personal and handheld devices has led to an explosion of peer-to-peer (P2P) usages. The P2P model is characterized by the fact that any station (STA) can potentially send wireless communications to any other STA directly, without having to route its transmissions through a special station such as an access point (AP).
To support these P2P usages, several network architectures at the media access control (MAC) layer are possible. For example, a centralized architecture such as an infrastructure basic service set (BSS) or a personal BSS (PBSS) can make use of their respective central network coordinators (AP and PCP, respectively) to setup these direct P2P links. These architectures as defined in the Institute of Electrical and Electronic Engineers (IEEE) 802.11 wireless local area network (WLAN) standard.
Another approach provided by the IEEE 802.11 WLAN standard is called the independent BSS (IBSS). This approach provides a distributed architecture, in which there is no central coordinator. Thus, an IBSS provides for any STA to communicate directly with another STA.
There are implications associated with choosing a centralized or a distributed architecture. In a centralized architecture provided by IEEE 802.11, only the central coordinator transmits beacon frames to synchronize all STAs in the networks. However, in a distributed architecture provided by IEEE 802.11, any STA can transmit beacon frames.
Interest in millimeter wave (e.g., 60 Gigahertz) networks is increasing. Such networks may make extensive use of beamformed (directional) transmissions. However, the employment of directional transmissions adds challenges to the transmission of beacons. For example, instead of sending a particular beacon only once, a STA may need to repeat a beacon as multiple directional transmissions in order to reach the full extent of the STA's transmission coverage.